[PATCHv2] nvme: module parameter to disable pi with offsets

[PATCHv2] nvme: module parameter to disable pi with offsets

[Keith Busch]

From: Keith Busch <kbusch@kernel.org>

A recent commit enables integrity checks for formats the previous kernel
versions registered with the "nop" integrity profile. This means
namespaces using that format become unreadable when upgrading the kernel
past that commit.

Introduce a module parameter to restore the "nop" integrity profile so
that storage can be readable once again. This could be a boot device, so
the setting needs to happen at module load time.

Fixes: 921e81db524d17 ("nvme: allow integrity when PI is not in first bytes")
Reported-by: David Wei <dw@davidwei.uk>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
v1->v2:

  Restrict the disabling only to the pi formats that have offsets

  Disable the pi_type in the head rather than just with blk-integrity

 drivers/nvme/host/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 84cb859a911d0..2054535d7c2ef 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -91,6 +91,10 @@ module_param(apst_secondary_latency_tol_us, ulong, 0644);
 MODULE_PARM_DESC(apst_secondary_latency_tol_us,
 	"secondary APST latency tolerance in us");
 
+static bool disable_pi = false;
+module_param(disable_pi, bool, 0444);
+MODULE_PARM_DESC(disable_pi, "disable protection information if it has an offset");
+
 /*
  * nvme_wq - hosts nvme related works that are not reset or delete
  * nvme_reset_wq - hosts nvme reset works
@@ -1915,6 +1919,8 @@ static void nvme_configure_metadata(struct nvme_ctrl *ctrl,
 		head->pi_type = id->dps & NVME_NS_DPS_PI_MASK;
 	if (!(id->dps & NVME_NS_DPS_PI_FIRST))
 		info->pi_offset = head->ms - head->pi_size;
+	if (info->pi_offset && disable_pi)
+		head->pi_type = 0;
 
 	if (ctrl->ops->flags & NVME_F_FABRICS) {
 		/*
-- 
2.43.5

Re: [PATCHv2] nvme: module parameter to disable pi with offsets

[Christoph Hellwig]

On Thu, Oct 24, 2024 at 08:27:02AM -0700, Keith Busch wrote:
> +static bool disable_pi = false;
> +module_param(disable_pi, bool, 0444);
> +MODULE_PARM_DESC(disable_pi, "disable protection information if it has an offset");
> +

The variable and module paramter are a bit misnamed now.  Also please
add a comment explaining why we have this seemingly odd flag.